- ID:
- ivo://CDS.VizieR/J/ApJ/526/788
- Title:
- Survey of infall motions toward starless cores
- Short Name:
- J/ApJ/526/788
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results of a survey of 220 starless cores selected primarily by their optical obscuration and observed in CS (2-1), N_2_H^+^ (1-0), and C^18^O (1-0) using the Northeast Radio Observatory Corporation (NEROC) Haystack 37 m telescope. We have detected 163 out of 196 sources observed in CS, 72 out of 142 in N_2_H^+^, and 30 out of 30 in C18O. In total, 69 sources were detected in both CS and N_2_H^+^. The isolated component of the N_2_H^+^ (1-0) spectrum (F_1_F = 0,1-1,2) usually shows a weak symmetric profile that is optically thin. In contrast, a significant fraction of the CS spectra show non-Gaussian shapes, which we interpret as arising from a combination of self-absorption due to lower excitation gas in the core front and kinematics in the core. The distribution of the normalized velocity difference ({delta}V_CS_) between the CS and N_2_H^+^ peaks appears significantly skewed to the blue (V_CS_ < 0), as was found in a similar study of dense cores with embedded young stellar objects (YSOs). The incidence of sources with blue asymmetry tends to increase as the total optical depth or the integrated intensity of the N_2_H^+^ line increases.
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- ID:
- ivo://CDS.VizieR/J/ApJS/253/44
- Title:
- Survey of SiO maser emission in oxygen-rich stars
- Short Name:
- J/ApJS/253/44
- Date:
- 01 Mar 2022 00:16:35
- Publisher:
- CDS
- Description:
- Circumstellar environments of oxygen-rich stars are among the strongest SiO maser emitters. Physical processes such as collisions, infrared pumping, and overlaps favor the inversion of level population and produce maser emission at different vibrational states. Despite numerous observational and theoretical efforts, we still do not have a unified picture including all of the physical processes involved in SiO maser emission. The aim of this work is to provide homogeneous data in a large sample of oxygen-rich stars. We present a survey of 67 oxygen-rich stars from 7 to 1mm, in their rotational transitions from J=1-0 to J=5-4, for vibrational numbers v from 0 to 6 in the three main SiO isotopologs. We have used one of the 34 m NASA antennas at Robledo and the IRAM 30m radio telescope. The first tentative detection of a v=6 line is reported, as well as the detection of new maser lines. The highest vibrational levels seem confined to small volumes, presumably close to the stars. The J=1-0, v=2 line flux is greater than the corresponding v=1 in almost half of the sample, which may confirm a predicted dependence on the pulsation cycle. This database is potentially useful in models which should consider most of the physical agents, time dependency, and mass-loss rates. As a by-product, we report detections of 27 thermal rotational lines from other molecules, including isotopologs of SiS, H_2_S, SO, SO_2_, and NaCl.
- ID:
- ivo://CDS.VizieR/J/A+AS/35/23
- Title:
- Survey of the Galactic Plane at 4.875 GHz
- Short Name:
- J/A+AS/35/23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A survey of the galactic plane was made with the Effelsberg 100-m telescope at a frequency of 4.875 GHz with a beamwidth of 2.6 arcmin. Table 1 is a list of 1186 radio sources in the surveyed area l = 357.5 to 60 deg, b = -1 to +1 deg. The primary calibration source was NGC 7027, which was assumed to have a flux density of 5.9 Jy (1 Jy = 10^-26^W.m-2.Hz-1). The uncertainty in day-to-day thermal calibration was +/- 5 to 10%.
- ID:
- ivo://CDS.VizieR/J/MNRAS/462/2747
- Title:
- S4 1030+61 VLBA observations, 2009-2014
- Short Name:
- J/MNRAS/462/2747
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the parsec-scale multifrequency properties of the quasar S4 1030+61 during a prolonged radio and {gamma}-ray activity. Observations were performed within Fermi {gamma}-ray telescope, Owens Valley Radio Observatory 40-m telescope and MOJAVE Very Long Baseline Array (VLBA) monitoring programmes, covering five years from 2009. The data are supplemented by four-epoch VLBA observations at 5, 8, 15, 24 and 43GHz, which were triggered by the bright {gamma}-ray flare, registered in the quasar in 2010. The S4 1030+61 jet exhibits an apparent superluminal velocity of (6.4+/-0.4)c and does not show ejections of new components in the observed period, while decomposition of the radio light curve reveals nine prominent flares. The measured variability parameters of the source show values typical for Fermi-detected quasars. Combined analysis of radio and {gamma}-ray emission implies a spatial separation between emitting regions at these bands of about 12pc and locates the {gamma}-ray emission within a parsec from the central engine. We detected changes in the value and direction of the linear polarization and the Faraday rotation measure. The value of the intrinsic brightness temperature of the core is above the equipartition state, while its value as a function of distance from the core is well approximated by the power law. Altogether these results show that the radio flaring activity of the quasar is accompanied by injection of relativistic particles and energy losses at the jet base, while S4 1030+61 has a stable, straight jet well described by standard conical jet theories.
- ID:
- ivo://CDS.VizieR/J/A+A/601/A12
- Title:
- S5 0716+714 VLBI K- and Q-band variability
- Short Name:
- J/A+A/601/A12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This study aims to search for the existence of intraday variability (IDV) of BL Lac object S5 0716+714 at high radio frequencies for which the interstellar scintillation effect is not significant. Using the 21-m radio telescope of the Korean VLBI Network (KVN), we present results of multi-epoch simultaneous dual-frequency radio observations. Single-dish observations of S5 0716+714 were simultaneously conducted at 21.7GHz (K-band) and 42.4GHz (Q-band), with a high cadence of 30-60min intervals. We observed four epochs between December 2009 and June 2010. Over the whole set of observation epochs, S5 0716+714 showed significant inter-month variations in flux density at both the K- and Q-bands, with modulation indices of approximately 19% for the K-band and approximately 36% for the Q-band. In all epochs, no clear intraday variability was detected at either frequency. The source shows monotonic flux density increase in epochs 1 and 3 and monotonic flux density decrease in epochs 2 and 4. In the flux density increasing phases, the flux densities at the Q-band increase more rapidly. In the decreasing phase, no significant flux density difference is seen at the two frequencies. The situation could be different close to flux density peaks that we did not witness in our observations. We find an inverted spectrum with mean spectral indices, {bar}{alpha}(S_{nu}_{prop.to}{nu}^-{alpha}^), of -0.57+/-0.13 in epoch 1 and -0.15+/-0.11 in epoch 3. On the other hand, we find relatively steep indices of +0.24+/-0.14 and +0.17+/-0.18 in epochs 2 and 4, respectively. We conclude that the frequency dependence of the variability and the change of the spectral index are caused by source-intrinsic effects rather than by any extrinsic scintillation effect.
- ID:
- ivo://CDS.VizieR/J/MNRAS/437/3265
- Title:
- Swift J1745-26 polarized jet
- Short Name:
- J/MNRAS/437/3265
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Swift J1745-26 is an X-ray binary towards the Galactic Centre that was detected when it went into outburst in 2012 September. This source is thought to be one of a growing number of sources that display `failed outbursts', in which the self-absorbed radio jets of the transient source are never fully quenched and the thermal emission from the geometrically thin inner accretion disc never fully dominates the X-ray flux. We present multifrequency data from the Very Large Array, Australia Telescope Compact Array and Karoo Array Telescope (KAT-7) radio arrays, spanning the entire period of the outburst. Our rich data set exposes radio emission that displays a high level of large-scale variability compared to the X-ray emission and deviations from the standard radio-X-ray correlation that are indicative of an unstable jet and confirm the outburst's transition from the canonical hard state to an intermediate state. We also observe steepening of the spectral index and an increase of the linear polarization to a large fraction (~50%) of the total flux, as well as a rotation of the electric vector position angle. These are consistent with a transformation from a self-absorbed compact jet to optically thin ejecta - the first time such a discrete ejection has been observed in a failed outburst - and may imply a complex magnetic field geometry.
- ID:
- ivo://CDS.VizieR/J/ApJS/208/25
- Title:
- Swift X-ray observations of 1FGL sources
- Short Name:
- J/ApJS/208/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have analyzed all the archival X-ray data of 134 unidentified (unID) gamma-ray sources listed in the first Fermi/LAT (1FGL) catalog and subsequently followed up by the Swift/XRT. We constructed the spectral energy distributions (SEDs) from radio to gamma-rays for each X-ray source detected, and tried to pick up unique objects that display anomalous spectral signatures. In these analyses, we target all the 1FGL unID sources, using updated data from the second Fermi/LAT (2FGL) catalog on the Large Area Telescope (LAT) position and spectra. We found several potentially interesting objects, particularly three sources, 1FGL J0022.2-1850, 1FGL J0038.0+1236, and 1FGL J0157.0-5259, which were then more deeply observed with Suzaku as a part of an AO-7 program in 2012. We successfully detected an X-ray counterpart for each source whose X-ray spectra were well fitted by a single power-law function. The positional coincidence with a bright radio counterpart (currently identified as an active galactic nucleus, AGN) in the 2FGL error circles suggests these sources are definitely the X-ray emission from the same AGN, but their SEDs show a wide variety of behavior. In particular, the SED of 1FGL J0038.0+1236 is not easily explained by conventional emission models of blazars. The source 1FGL J0022.2-1850 may be in a transition state between a low-frequency peaked and a high-frequency peaked BL Lac object, and 1FGL J0157.0-5259 could be a rare kind of extreme blazar.
- ID:
- ivo://CDS.VizieR/J/MNRAS/372/741
- Title:
- SXDF 100{mu}Jy catalogue
- Short Name:
- J/MNRAS/372/741
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe deep radio imaging at 1.4GHz of the 1.3-deg^2^ Subaru/XMM-Newton Deep Field (SXDF), made with the Very Large Array in B and C configurations. We present a radio map of the entire field, and a catalogue of 505 sources covering 0.8deg^2^ to a peak flux density limit of 100uJy. Robust optical identifications are provided for 90 per cent of the sources, and suggested identifications are presented for all but 14 (of which seven are optically blank, and seven are close to bright contaminating objects). We show that the optical properties of the radio sources do not change with flux density, suggesting that active galactic nuclei (AGN) continue to contribute significantly at faint flux densities. We test this assertion by cross-correlating our radio catalogue with the X-ray source catalogue and conclude that radio-quiet AGN become a significant population at flux densities below 300uJy, and may dominate the population responsible for the flattening of the radio source counts if a significant fraction of them are Compton-thick.
- ID:
- ivo://CDS.VizieR/VIII/78
- Title:
- Sydney University Molonglo Sky Survey (SUMSS)
- Short Name:
- VIII/78
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Sydney University Molonglo Sky Survey (SUMSS) is being carried out at 843MHz with the Molonglo Observatory Synthesis Telescope (MOST) in its upgraded wide-field capability. The survey consists of 4.3x4.3{deg} mosaic images with 45x45''cosec{delta} resolution, covering 8000 square degrees from -30 degrees declination southwards. The survey resolution and sensitivity (1-sigma noise limit 1mJy) are well-matched to the NRAO VLA Sky Survey (NVSS) so that together NVSS and SUMSS will provide a complete survey of the radio sky. The version 1.7 (01-Jun-2006) of the catalogue consists of 205676 radio sources made by fitting elliptical gaussians in 671 SUMSS mosaics to a limiting peak brightness of 6mJy/beam at declination <-50{deg}, and 10mJy/beam at declination >-50{deg}. Positional accuracies are 1-2'' for sources with S_p_>=20mJy/beam, and are always better than 10''. The internal flux density scale is accurate to 3%. Image artefacts have been classified using a decision tree, which correctly identifies and rejects spurious sources in over 96% of cases. See the SUMSS site at http://www.astrop.physics.usyd.edu.au/sumsscat/ for details about all versions of the SUMSS, and an access to the mosaic images.
- ID:
- ivo://CDS.VizieR/VIII/81B
- Title:
- Sydney University Molonglo Sky Survey (SUMSS V2.1)
- Short Name:
- VIII/81B
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Sydney University Molonglo Sky Survey (SUMSS) is carried out at 843MHz with the Molonglo Observatory Synthesis Telescope (MOST) in its upgraded wide-field capability. The survey consists of 4.3x4.3{deg} mosaic images with 45x45''cosec{delta} resolution, covering 8000 square degrees from -30 degrees declination southwards with |b|>10{deg}. The survey resolution and sensitivity (1-sigma noise limit 1mJy) are well-matched to the NRAO VLA Sky Survey (NVSS) so that together NVSS and SUMSS provide a complete survey of the radio sky. The version 2.0 (08-Aug-2007) of the catalogue consists of 210412 radio sources made by fitting elliptical gaussians in 633 SUMSS mosaics to a limiting peak brightness of 6mJy/beam at declination <-50{deg}, and 10mJy/beam at declination >-50{deg}. Positional accuracies are 1-2'' for sources with S_p_>=20mJy/beam, and are always better than 10''. The internal flux density scale is accurate to 3%. Image artefacts have been classified using a decision tree, which correctly identifies and rejects spurious sources in over 96% of cases. See the SUMSS site at http://www.astrop.physics.usyd.edu.au/sumsscat/ for details about all versions of the SUMSS, and an access to the mosaic images. The version 2.1 (from 2008-03-11) corrects a bug in 2.0 in which some bright (S>500 mJy) sources were missing from the catalogue.
